1. Field of the Invention
This invention relates generally to improvements in infusion pumps such as those used for controlled delivery of medication to a patient. More specifically, this invention relates to an improved motor system for infusion pumps and to improved medication delivery.
2. Description of the Related Art
Infusion pump devices and systems are relatively well-known in the medical arts, for use in delivering or dispensing a prescribed fluid medication such as insulin to a patient. In one form, such devices comprise a relatively compact pump housing adapted to receive a syringe or reservoir carrying a prescribed fluid medication for administration to the patient through infusion tubing and an associated catheter or infusion set.
The infusion pump includes a small drive motor connected via a suitable transmission such as a lead screw assembly to advance a reservoir piston to administer the medication to the user. Programmable controls can operate the drive motor continuously or at periodic intervals to obtain a closely controlled and accurate delivery of the fluid medication over an extended period of time. Such infusion pumps are utilized to administer insulin and other medications, with exemplary pump constructions being shown and described in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653 and 5,097,122, which are incorporated by reference herein.
Infusion pumps of the general type described above can provide significant advantages and benefits with respect to accurate delivery of medication or other fluids over an extended period of time. However, the infusion pump should also be designed to be compact, and readily carried by the user by means of a belt clip or the like. If so, important medication can be delivered to the user not only with precision and in an automated manner, but also with reduced restriction on the user""s mobility and life-style.
In accordance with one aspect of the inventions, a drive motor for an infusion pump system includes a novel outer housing which includes a unitary member which defines a cavity adapted to receive a winding wherein the housing cavity has a length at least as long as a length of the winding. In the illustrated embodiment, the housing unitary member has an opening at one end adapted to receive a housing end member which has a guide track for an armature. The guide track of the housing end member extends at least partially into a magnetic field generation area of the winding. An armature is slidingly received in the housing end member guide track, and is adapted to slide along the housing end member guide track in response to a magnetic field generated in the magnetic field generation area. As explained in greater detail below, such an arrangement facilitates assembly and disassembly of the motor for fabrication, inspection and repair purposes yet also facilitates proper alignment of the components when assembled.
In the illustrated embodiment, the housing defines a push member guide track aligned with the end armature guide track. The drive motor has a push member slidingly received in the push member guide track and is positioned to be engaged by the armature and to slide along the push member guide track in response to engagement by the armature. In accordance with another aspect of the present inventions, the push member has an engagement face which is at least 40% of the width of the armature engagement face. In still another aspect of the present inventions, the armature may have a stem portion which is slidingly received in the armature guide track and a head portion positioned to engage the push member wherein the armature head portion is wider than the armature stem portion and has a length at least 10% of the winding length. In yet another aspect of the present inventions, the push member may have a single diameter cylindrical shape and the push member guide track may similarly have a single diameter cylindrical shape which is sized to slidingly receive the push member. It is believed that one or more of these features can increase the actuation force provided by the motor yet maintain a compact size.
There are additional aspects to the present inventions as discussed below. It should therefore be understood that the preceding is merely a brief summary of some embodiments of the present inventions. It should further be understood that numerous changes to the disclosed embodiments can be made without departing from the spirit or scope of the inventions. The preceding summary, therefore is not meant to limit the scope of the inventions. Rather, the scope of the inventions is to be determined only by the appended claims and their equivalents.